Vane type network attenuation means



Feb. 11, 1958 E. c. DENCH ETAL 2,323,335

VANE TYPE NETWORK ATTENUATION MEANS Filed Oct. 21, 1955 INVENTORSZ thy A20 C. flaw-H /i 160 A. AAMO) A TTogEY United States Patent 2,823,335 VANE TYPE NETWORK ATTENUATION MEANS Edward C. Dench, Needham, and Richard A. Handy,

Belmont, Mass., assignors, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Application October 21, 1955, Serial No. 542,111 1 Claim. (Cl. 31539.3)

This invention relates to attenuating means for a vane type network and more particularly, to a magnetron traveling wave amplifier incorporationg a vane type network with attenuating means.

This invention describes means for obtaining a desired attenuation characteristic in a vane type transmission network. Such attenuation means m-ay be employed in traveling wave amplifiers incorporating a vane type structure for the purpose of limiting the gain of the amplifier to prevent unwanted self oscillation. It is particularly suitable for use in magnetron traveling wave amplifiers, which are especially susceptible to self oscillation, due to the relatively high residual coupling of output back to input.

It is therefore an object of this invention to provide attenuation means for a vane type network.

It is a further object of this invention to provide a traveling wave amplifier employing a vane type network incorporating attenuating means.

It is a still further object of this invention to provide a magnetron traveling wave amplifier employing a vane type network incorporating attenuating means.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing wherein:

Fig. 1 is a plan view of a vane type magnetron embodying the principles of this invention,

Fig. 2 is an elevation section of the magnetron shown in Fig. 1, and

Fig. 3 is a plan view of a modification of the magnetron shown in Figs. 1 and 2.

Referring now to Figs. 1 and 2, magnetron anode cylinder is concentrically disposed about magnetron cathode 12. Planar vanes 14 are supported by anode cylinder 10 and are arcuately spaced at predetermined intervals over a given circumferential portion thereof. Vanes 14 are oriented with the planes thereof parallel to the axis of cylinder 10 and extend radially therefrom partway to cathode 12. Vanes 14 define a series of similarly configured resonant cavities each of which exists between adjacent vanes. Therefore the series of resonant cavities lie in a sector of cylinder 10 which has an arcuate extent which coincides with the given circumferential portion in which vanes 14 are located.

Input means 16 are provided for introducing a signal into the resonant cavity located at one end of the series and output means 18 are provided for extracting a signal from the resonant cavity located at the other end of the series.

It will be noted that output means 18 is coupled back to input means 16 by the remaining sector of anode cylinder 10. This coupling, which may provide regeneration resulting in unwanted self-oscillation, is minimized by making the arcuate extent of this remaining sector large compared to the spacing between adjacent vanes 14. In addition, attenuating means are provided for limiting the gain of the magnetron amplifier.

The attenuating means consists of ring 20 having a circumferential length coextensive with the given portion in which vanes 14 are located. Ring 20 is composed of a 2,823,335 Patented Feb. 11, 1958 lossy material such as graphite. The lossy material is not limited to graphite, however, but may be aquadag, lossy ceramic, water (circulated in glass), etc.

The axial thickness of graphite ring 20 should be as small as possible consistent with considerations of skin depth to provide a large ratio of surface area to volume and ring 20 should be connected to anode cylinder 10 by means having high heat conduction in order to dissipate the heat which is generated in ring 20 during operation.

One way (not shown) of connecting ring 20 to anode cylinder 10 which provides high heat conduction is to copper plate ring 20, then silver solder a copper ring of the same circumferential length and radial width thereto, soldering the outside surface of this copper ring to the adjacent inside wall of anode cylinder 10.

The attenuation provided by graphite ring 20 depends on the width thereof, increasing with width. By using a wide ring, attenuations up to 30 db may be obtained.

The attenuation characteristic of the network is fairly flat with frequency over the operating passband. The presence of graphite ring 20, in addition to preventing selfoscillation of the magnetron amplifier, also provides greater interaction between the space current of the magnetron and the resonant cavities formed by vanes 14.

The input and output impedances remain fairly constant with changes in frequency. However, better matching may be obtained, discontinuous effect of the attenuative material may be lessened, and distribution of power on the anode for best interaction may be improved, by tapering the width of the graphite ring, as shown by graphite ring 20' in Fig. 3 wherein like elements are identified by identical reference numerals.

This invention is not confined to circular geometry, as employed in the magnetron, but may be used in a linear vane type structure, or a vane type structure of any other shape, if so desired.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

We claim:

In a traveling wave amplifier, a cylindrical anode, a series of flat similarly shaped conductive vanes secured to the inner surface of said anode, parallel to the axis of said anode, and at regularly spaced intervals about a sector of the circumference of said anode whereby the remaining sector of the circumference has an arcuate extent which is substantially greater than the interval between vanes and whereby said vanes extend radially part way toward the axis of said anode to define a series of similarly configured resonant cavities, a cathode disposed coaxially within said anode and spaced from the ends of said vanes, means secured to said anode at one end of said series and adapted for the application of an input signal into the resonant cavity at the one end of said series, means secured to said anode at the other end of said series and adapted for the extraction of an output signal from the resonant cavity at the other end of said series, an arcuate fiat attenuating means of the same radius as the inner surface of said anode and of arcuate length equal to the sector occupied by said vanes, one flat surface of said attenuating means engaging one edge of each of said vanes, and means having good heat conductivity connecting the peripheral surface of said attenuating means with the inner surface of said anode.

References Cited in the file of this patent UNITED STATES PATENTS 2,660,689 Touraton et al Nov. 24, 1953 2,673,306 Brown Mar. 23, 1954 2,740,068 Robertson et al. Mar. 27, 1956 

